FCoE (Fibre Channel over Ethernet) is a protocol for transmitting data of an FC (Fibre Channel) over Ethernet (registered trademark, to be interpreted in the same way hereinafter). There is a technology of using the FCoE to cause a LAN (Local Area Network) and a SAN (Storage Area Network) to converge on the same physical network. The LAN connects a server and a client, while the SAN connects the server and a storage device. The network constituted by the converged LAN and SAN is referred to as a “converged LAN/SAN network”.
The converged LAN/SAN network will be described with reference to FIG. 10. FIG. 10 is a diagram illustrating an example of the converged LAN/SAN network. As illustrated in FIG. 10, a converged LAN/SAN network 900 includes relay devices 901 to 907 that relay an IP (Internet Protocol) packet and an FCoE packet. L3 switches 700a and 700b, information processing devices 800a to 800c, and a storage device 800e are connected to the converged LAN/SAN network 900.
In this converged LAN/SAN network 900, as illustrated in FIG. 10, each relay device is connected to adjacent relay devices to constitute a multipath network. All paths in the multipath network are active; none of the paths is on standby. This enables each relay device to transfer a packet through any path, thus increasing a bandwidth thereof.
To transfer an IP packet or an FCoE packet, each relay device in the converged LAN/SAN network 900 selects a path with the lowest link cost through TRILL (Transparent Interconnection of Lots of Links). To transfer an FCoE packet from the information processing device 800a to the storage device 800e in the example illustrated in FIG. 10, the converged LAN/SAN network 900 selects a path that goes through the relay device 901, the relay device 902, and the relay device 903.
Patent Document 1: Japanese Laid-open Patent Publication No. 2006-268625
Patent Document 2: Japanese Laid-open Patent Publication No. 2009-303090
Patent Document 3: Japanese National Publication of International Patent Application No. 2011-508523
In the above-described related art, however, there is a problem in that the bandwidth is not effectively used.
More specifically, the converged LAN/SAN network always selects a shortest path, although all the paths in the network are active. Therefore, congestion may occur upon concentration of IP packets and FCoE packets at a port of the relay device on the shortest path.
An example will be described where, in FIG. 10, an FCoE packet is transferred from the information processing device 800b to the storage device 800e at the same time as another FCoE packet is transferred from the information processing device 800a to the storage device 800e. For easy understanding of the description, it is assumed that each path has a bandwidth of 10 GB.
In the case where 10 GB information is transferred from the information processing device 800a and 7 GB information is transferred from the information processing device 800b, the relay device 902 transfers the 17 GB information to the relay device 903. As a result, the relay device 902 transfers, to the relay device 903, the information of the size exceeding the bandwidth, thus causing congestion between the relay device 902 and the relay device 903.
Upon detecting the occurrence of congestion, the relay device 903 prevents abandonment of the FCoE frame in order to secure the order of data. For example, the relay device 903 notifies the information processing device 800a and the information processing device 800b of the occurrence of congestion by transmitting CN (Congestion Notification) frames thereto. Upon receiving the CN frames, the information processing device 800a and the information processing device 800b adjust, through traffic shaping, the transfer amount so as not to generate a frame loss, thereby controlling the bandwidth.